Append in str the Eiffel coding of the character (Table in chapter 25 of ETL, page 423).%%%%%%%%

When the % letter notation exists, it is returned in priority: '%N' gives "%N", '%T'
gives "%T", etc.
When % letter notation does not exists (not in the ETL table), numbered coding
used ("%/1/", "%/2/" etc).

is " has no compiler-defined `deep_twin' or `is_deep_equal' because the corresponding allocated size is not part of the NATIVE_ARRAY object. The client class of this NATIVE_ARRAY type is supposed to use a `capacity' attribute which contains the corresponding number of allocated items (see STRING or ARRAY for example)."